He was visiting Southbridge Domain playground with his grandmother Angela Slade and eight-year-old cousin Emily when the incident happened.
Angela said the visit to the park suddenly became a life-and-death situation after Jayden was attracted to water around the travelling roto-rainer irrigator in hot weather.
He was struck as he stood up after slipping.
Angela said at first she had not noticed Jayden had wandered about 15m away to play under the irrigator on an adjoining rugby field.
As she unpacked food onto a picnic table, she heard “a horrible, horrible scream”.
Angela said she had earlier pointed out to the children a single caution sign nearby saying ‘Potentially Dangerous Equipment’, but this had obviously not been enough to keep Jayden away.
Jayden was in extreme pain after the accident and began vomiting. He was taken to Christchurch Hospital by ambulance.
Last week he had a craniotomy, where a 10cm long piece of bone from his forehead was removed and replaced with a plate.
He may have to have more surgeries to replace the plate as he grows.
He was discharged at the weekend, and is expected to make a full recovery.
He will be at school only part-time throughout term one.
Whittaker said she was glad to hear the Selwyn District Council had removed all such irrigators from operation in parks and reserves.
She said while the caution sign had been pointed out to Jayden, he would not have absorbed the information due to a learning disability and dyslexia.
“I don’t want it to happen to anybody else,” she said.
"This type of irrigator is common in rural areas and has been used by the council for around 30 years without incident to our knowledge," Washington said.
"We plan to replace them with modern technology water cannon type irrigators, which will minimise any future risk to the public.”
